In various applications including televisions, projectors, monitors, camcorder viewfinders, printing devices, and other applications that detect or project colors, a spectrophotometer or calorimeter may be used to detect and measure a spectrum of colors. Colorimeters may determine colors using one or more sets of photodetectors and color filters each configured to detect a predetermined spectrum of wavelengths. The filters often have similar bandwidths and generally are chosen so that they span the visible spectrum.
However, the resulting performance of many such filters does not correspond well to the response of Commission Internationale de l'Eclairage (CIE) observer color-matching functions at all wavelengths. The lack of correspondence at a given wavelength can be quite large, particularly for spectra that vary rapidly with wavelength or spiky spectra.
Some calorimeters use few photodiodes and filters to determine colors and consequently require that the filter responses closely correspond with the color-matching functions for accurate color detection. The expense of these filters increases with increased correspondence to the standard. Other colorimeters use more filters of narrower, but similar, bandpass to cover the visible spectrum.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.